Related notes:

Already resolved in the ED:

"""
If a size property declaration is qualified by a ‘width’, ‘height’, ‘device-width’, ‘device-height’, ‘aspect-ratio’, ‘device-aspect-ratio’ or ‘orientation’ media query [MEDIAQ] (or other conditional on the size of the paper), then the declaration must be ignored. Media queries do not honor ‘size’: they assume the paper size that would be chosen if no @page rules were specified.
"""

This is consistent with how Media Queries generally work:

"""
To avoid circular dependencies, it is never necessary to apply the style sheet in order to evaluate expressions. For example, the aspect ratio of a printed document may be influenced by a style sheet, but expressions involving ‘device-aspect-ratio’ will be based on the default aspect ratio of the user agent.
"""